totm nov 2023 SpaceX Discussion Thread

[sevenperforce]

36 minutes ago, JoeSchmuckatelli said:

I can accept that - but the foil wrapped stuff and some kind of tubing went up too.  At the 1:40 mark - the stuff on the right catches fire.  Not educated enough to know what it was - but clearly the ship continued to operate without.

It didn’t catch fire; that was just hydrocarbon deposition undergoing combustion in a low-pressure atmosphere.

36 minutes ago, JoeSchmuckatelli said:

On another note: why would they not deploy the legs earlier?  Even if they had collapsed given the rate of descent there at the end... might they not have acted like a bumper and increased the chance of less than complete destruction?

My guess is that the legs have an experimentally-determined rating for impact velocity and the simplest way to trigger deployment is at some predetermined multiple of that velocity, like 3x. So the legs deploy when the ship reaches a velocity which is less than 3x the maximum survivable impact velocity. 

[.50calBMG]

It really is amazing how close they got on the first try, way better than the early F9 attempts. I was guessing that the flip would be mistimed and they would pancake, but it was about as close to perfect as it could have gotten. I was telling my coworkers that it would probably be 5-6 flights before they landed one, now I think its probably closer to 2-3. once again, SpaceX is really good at doing the impossible. o7

[tater]

I'd not be surprised to see SN9 land, honestly.

And it's right there, good to go.

[JoeSchmuckatelli]

14 minutes ago, sevenperforce said:

It didn’t catch fire; that was just hydrocarbon deposition undergoing combustion in a low-pressure atmosphere.

...

Okay, wait - hold on.  Something man-made (not deposits) burned.  Look at +00:42 on the video.  To the right of the engines in the engine view - there are a few foil wrapped somethings on the inside of the skirt.  As you watch from that point, you can see the foil flapping.

The flare out starts @ +01:42.  You can see the flames go right to the foil packets.  Then they sort-of independently catch fire at +01:49.  At +01:55 you start to see some of the burned stuff fall out.

So I don't know what it was - and again, it did not affect the flight... but something burned.

[magnemoe]

10 minutes ago, sevenperforce said:

My guess is that the legs have an experimentally-determined rating for impact velocity and the simplest way to trigger deployment is at some predetermined multiple of that velocity, like 3x. So the legs deploy when the ship reaches a velocity which is less than 3x the maximum survivable impact velocity. 

Guess the touchdown code is from falcon 9 first stage, and on an falcon 9 you need to extend the leg late and while going pretty slow because they have so much drag at the base, assume its even an speed limit as you could not extend the leg if drag is too high. 

[tater]

 

[JoeSchmuckatelli]

My kid keeps asking me this; anyone know how much SN8 cost?

(I know you can't measure total input of time, effort, etc: what he's interested in is what a Starship like that might run on the open market.

 

 

I think he's planning something

[tater]

42 minutes ago, JoeSchmuckatelli said:

My kid keeps asking me this; anyone know how much SN8 cost?

An order of magnitude less than an SLS booster? Maybe and order of magnitude cheaper than a single RS-25 for SLS?

[Delay]

Only watched the replay now. That was amazing! They almost stuck the landing on the first attempt!

Also, you just have to appreciate how persistent SpaceX (and I guess in particular, Elon) is. SN8 just went up in a huge fireball, and the stream shows "SN9 is up next!".

[KSK]

Any bets on whether they'll reuse the nosecone from SN8 just because?  That thing survived an off-nominal landing - it's clearly built to last! Likewise with that landing pad.

Seriously though - the flight happened too late for me to catch it last night but damn if that wasn't an *awesome* start to the day!

[RealKerbal3x]

I just scrolled through the news on my phone and I saw exactly what I expected: media companies insisting that the flight was a failure because EXPLOSION.

Sigh

[KSK]

43 minutes ago, RealKerbal3x said:

I just scrolled through the news on my phone and I saw exactly what I expected: media companies insisting that the flight was a failure because EXPLOSION.

Sigh

And they probably always will. Objectively, it's quite difficult to paint a fiery explosion as anything other than a failure without going into a fair bit of detail and justification - which most publications or their readers aren't interested in. I did like the one article which reassured everyone that the flight was uncrewed - and that need for a human-interest angle also says a fair bit about media priorities.

As for myself, I have these words:

SpaceX... the final frontier.
That was the voyage of the Starship SN8.
It's mission:

To demonstrate controlled falling with style;
To relight engines and perform an experimental kickflip;
To boldly 'splode, like no rocket has 'sploded before!

[RealKerbal3x]

6 minutes ago, KSK said:

SpaceX... the final frontier.
That was the voyage of the Starship SN8.
It's mission:

To demonstrate controlled falling with style;
To relight engines and perform an experimental kickflip;
To boldly 'splode, like no rocket has 'sploded before!

SN8 died so that future Starships can fly

Go SN9!

Edited December 10, 2020 by RealKerbal3x

[RealKerbal3x]

 

[Nothalogh]

11 hours ago, JoeSchmuckatelli said:

why is Senate's burn so clean?

Because a senate is mostly hot air

[sh1pman]

4 hours ago, Delay said:

SN8 just went up in a huge fireball, and the stream shows "SN9 is up next!".

*SN9 looks at the wreckage nervously*

[Codraroll]

Upon rewatching, it looks like the impact was a little harder than I assumed at first. When the rocket touches down, the nose appears to "explode", at least it leaks gas everywhere. Wonder if that's the water hammer effect in the RCS system sending RCS gas out of all available openings, or something more sinister like welds tearing apart? 

[sevenperforce]

3 hours ago, Codraroll said:

Upon rewatching, it looks like the impact was a little harder than I assumed at first. When the rocket touches down, the nose appears to "explode", at least it leaks gas everywhere. Wonder if that's the water hammer effect in the RCS system sending RCS gas out of all available openings, or something more sinister like welds tearing apart? 

It’s catastrophic weld failure. Remember that the tanks are pressed to a pretty significant extent with warm methane and warm oxygen. In fact, they are at a higher pressure than some pressure-fed rockets. So when the spaceship hits the ground, instant deformation of the steel skin results in that internal pressure busting straight through the skin like aluminum foil. 

The fireball was mostly the gases mixing and igniting, not the liquid. There was very little liquid propellant in the tanks at this point. 

6 hours ago, Nothalogh said:

Because a senate is mostly hot air

WHY DON’T I HAVE ANY MORE REACTIONS TODAY

Edited December 10, 2020 by sevenperforce

[paul_c]

Brilliant flight, Elon did really well even with the WASD controls and didn't muddle them up once, including the flipover and just before the landing! I think he forgot to press SPACE bar at some point moments before though.

But seriously, without knowing the exact profile of the engines firing/shutting down/restarting, all we can do is guess at the detailed planned flight path, and the corresponding engine and control inputs planned to execute the plan. It looks like they clearly planned to shut engines down at different times, and we saw that clearly working; and the sideways translation and attitude changes without much gain/loss in altitude. We don't know - and I suspect they didn't either, until yesterday - what the various hot gases, or exhausts, will do in the airflow when doing these not-seen-before-by-a-rocket maneouvers and whether they'll have a negative influence on other portions of the flight. My concern is the fuel flow during the landing phase is a new thing to get to grips with, and it was designed into the rocket using separate tanks (which it did switch over to) but the pressure/flowrates didn't work out as expected. Not easy to simulate without actually putting another rocket through a flight. Hopefully there's just a tweak or two needed (I hope Elon put the yellow pipes in with the arrows facing the right way) but it might need a more thorough redesign???

[RealKerbal3x]

On 12/8/2020 at 9:19 PM, Delta dart said:

@RealKerbal3x You should change your location to 12,500m above Boca Chica.

Done now, and I've changed my profile pic too

[Serpens Solidus]

This is the only wide angle view i could find:

Hopefully we will get better ones soon. Look how slow it falls!

[tater]

19 minutes ago, Serpens Solidus said:

Look how slow it falls!

Yeah, remarkable. We knew it would be slow (from SpaceX sims), but it's still unexpected when you actually see it.

[RealKerbal3x]

This is restoring my faith in humanity:

[Kerwood Floyd]

Has anyone heard how high it actually got?

 

[RealKerbal3x]

I'm surprised nobody has posted this yet.